A combination of the heavy fall schedule, the decision to focus on mostly new sketches, post-election blues, Hurricane Sandy, integrating the new cast, etc., taken altogether, I suspect, is the reason. If you watch closely, the show had been straining at the seams the previous three episodes. Lots of production glitches, the sketch premises got more and more basic, etc. I've been expecting that they'd come back after the holidays with some degree of mid-season revamping, and the longer break seems a sign of that.